1. Field of the Invention
This invention relates to a two component explosive composition particularly adapted for field mixing.
2. Description of the Prior Art
There are in the prior art various two component explosives, in which each component by itself is non-detonable, and the two components can be mixed together to form an explosive composition. Quite commonly one of the components is a solid and the other a liquid, with the mixing being accomplished by pouring the liquid into the solid. One of the most common two component explosives is made by adding about 5% fuel oil to about 95% ammonium nitrate to make an explosive mixture commonly called "ANFO". However, for detonation, this mixture requires a powerful booster and critical diameters of approximately three inches or more.
A common practice is to detonate an explosive in a borehole that is drilled into a ground formation. One method of placing the explosive in the borehole is to prepackage the explosive in a number of elongate tubular packages, and then arrange these packages in end to end relationship to form an explosive train that is inserted into the borehole. A detonator is inserted into the end cartridge to initiate the explosive reaction.
An explosive composition suitable for field mixing and detonation in boreholes, as described above, is that disclosed in U.S. Pat. No. 3,768,410, issued Oct. 3, 1973 and assigned to the assignee of the present invention. In this explosive composition there is a first solid component made up of ammonium nitrate or mixtures of ammonium nitrate with ammonium perchlorate or the like, and a second liquid component made up of hydrazine and water. The ratio of the liquid to solid component is about one to two parts liquid component to about 15 parts solid component, with the preferred ratio being about 1 to 10. For maximum safety, the amount by weight of water in the liquid component is at least about equal to, or slightly greater than, the amount of hydrazine. This ratio is particularly advantageous since the hydrazine with at least an equal amount of water can be shipped by common commercial transportation as a separate component without hazardous comodity labels, as can the solid component which is ammonium nitrate. A package of this explosive mixture with a diameter down to about 11/2 inches can be detonated in a borehole by use of a blasting cap.
By way of further background information, in U.S. Pat. No. 3,419,443, Maes, there is disclosed an explosive composition comprising hydrazinium nitrate, hydrazine and ammonia, with or without hydrazinium perchlorate. This explosive composition has been formulated as a two component explosive, where ammonium nitrate is the solid component and hydrazine is the liquid component, in a ratio of about two parts solid to one part liquid component. In some formulations a portion of the ammonium nitrate is dissolved in the liquid hydrazine in the premix condition. However, this is done primarily to lower the freezing point of the liquid component. A second reason for doing this is that adding hydrazine to ammonium nitrate gives off gaseous ammonia which can cause the mixture to foam or bubble to an undesired extent. By premixing some of the ammonium nitrate with the hydrazine, some of the ammonia can be boiled off in the preparation of the premix components, so that this foaming can be reduced in the mixing of the two components to make the explosive composition. Other related patents are Audrieth et al, U.S. Pat. No. 2,943,927; Audrieth et al, U.S. Pat. No. 2,704,706; Hradel, U.S. Pat. No. 3,124,495; Stengel, U.S. Pat. No. 2,978,864; Stengel et al, U.S. Pat. No. 3,061,489; and Rank et al, U.S. Pat. No. 3,558,749.